The Bears now are in the midst of a similar transition as they move away from the Brian Urlacher era. Though the Bears decided to part ways with Urlacher before his retirement, Wednesday's news drove home the fact that the team will be without the linebacker next season for the first time in 13 years.

"You got to go back and look at it, what happened when Mike Singletary retired?" Rivera told NFL Network's Stacey Dales. "What happened to the Bears for a while? They were trying to find that next guy. That was the hard thing was, they were they were trying to find that next guy. That'll happen now, they'll try and find that next guy. Who's going to be that next middle linebacker and that great Bear player?"

Rivera knows firsthand the challenge the Bears face in replacing Urlacher. Rivera was the Bears' defensive coordinator from 2004 to 2006 and saw Urlacher win NFL Defensive Player of the Year honors in 2005.

"For his era, the era that I coached him, (he) goes down of one of the all-time greats," Rivera said. "I say that because he just epitomized what a Bears middle linebacker is."

Rivera wasn't the only person with ties to the Bears organization to reflect on Urlacher's legacy in Chicago.

"He meant so much to our football team, to the franchise," former Bears general manager Jerry Angelo told WSCR-AM on Wednesday. "He just handled himself with total class. It's hard to imagine that you could have the type of work ethic that Brian had, given all his God-given talents, but he worked as hard as any player we had in that locker room. You thought he was a college free agent the way he worked every day."

Said former Bears linebackers coach Bob Babich, now the Jacksonville Jaguars' defensive coordinator: "I was very fortunate to coach such a great person, player and leader, on and off the field. The nine years with Brian were the most rewarding coaching experience of my career. Not only did I challenge him daily, he helped me become a better coach and person.

"He will go down in history as one of the best middle linebackers in NFL history and is a future Hall of Famer," Babich added, via The Florida Times-Union. "He revolutionized the game as far as middle linebacker play. We think of him as not only a great player but a part of our immediate family and always will."